That's the question Matt Miller asks on Tom Paine.com. Well, that's the headline to his article, and a silly question. A market is amoral, it's just an inanimate thing, a framework for action. Actions, of course, may be questioned on the basis of morality. Markets may then be used for moral or immoral actions. But Miller gets to the real question in the article:

Is the distribution of income produced by the free market presumptively moral?
People who say "yes" tend to believe there's a necessary connection between accepting markets as the best means of organizing economic life, and accepting the results that markets produce as making moral sense....
On this view, market outcomes reward virtues and qualities that it is right to reward -- things like work, responsibility, thrift, innovation and risk-taking. You can reject markets, they say, but you can't accept them (as most Americans do) and then deny that their distributional results have some claim to being considered presumptively fair.

Ah, yes I can. I will emphatically state that life, and markets, are unfair. Some people become wealthy without merit, some are poor without blame. But no one has come up with any economic system that guarantees completely merit based outcomes. Miller continues:

We also note the obvious: The distribution of income in free markets is affected dramatically by factors beyond the virtues cited above -- such as a person's inherited brains, health, talents, wealth and looks, as well as the family into which one is born and the early schooling one is given.
These are things for which people can't take credit or be blamed. Given how heavily these morally arbitrary factors influence the distribution if income, it's silly, we argue, to think that market outcomes could be presumptively moral.

Let me repeat, actions are subject to moral judgement. Outcomes are amoral, although outcomes may be greatly affected by the morality of the actions from whence they are produced. Let's examine, briefly, the actions necessary to circumvent free markets, namely, someone must forcibly curtail the free interaction of people. That is immoral in itself. The moral superiority of free markets is based on the morality of actions, not results. That means if the actors in a market are acting honestly, morally, interference in that market is immoral, as that interference constitutes a violation of the personal rights of the actors.